Electric switch



Oct. 28, 1941. J. c. ENGLISH ELECTRIC SWITCH Original Filed June 28 1939 mv H R H m J N 1 m U m I km W m n I E A w a x N H W! I M R 0 W Q Q \Q w E g mg Patented Oct. 28, 1941 ELECTRIC swrron John C. English, Cedar Rapids, Iowa,

Johnson Gas Appliance Company,

assignor to Cedar Rapids, Iowa, a corporation of Delaware Original application June 28, 1939, Serial No.

281,549. Divided and this application February 17, 1940, Serial No. 319,501

Claims. (Cl. 175-415) This invention relates to electric switches and has particular reference to a switch adapted for operation by small differentials of fluid pressure, either hydraulic or pneumatic, or both.

This application is a division of application Serial Number 281,549 filed June 28, 1939 by John C. English on Ignition control means for fuel burners.

In some fields, as for instance control systems for fluid fuel burners, it is desirable that a switch be provided which may be located at some distance from the burner and yet operative by small differentials in hydraulic or gas pressure within the system.

It is, therefore, among the objects of my invention to provide an electric switch which will satisfactorily meet the requirements above set forth and which is operative to open or close a circuit in response to quite small differentials in pressure, and in which corrosion and deterioration of the electric contacting means is practically eliminated.

Another object of my invention is to provide a switch which may be operated either by differences of pressure above or below atmospheric pressure, or by differences between atmospheric pressure and a pressure above or below atmospheric pressure.

Another object of my invention is to provide a switch which may be used intermittently for separate operations by utilizing the initial and subsequent pressure of the mechanism upon which it operates to open and close said switch.

Another important object of my invention is to provide a quick acting switch which may be placed at a position remote from the device upon which it operates.

Another object of my invention is to very materially reduce the amount of wiring required in an electrical switch.

A further object of my invention is to provide an electrical switch which is inoperative unless there is sufficient pressure differential present within the means from which the switch is to be operated and to provide means for adjusting the operating differential.

Still another object of my invention is to provide an electrical pressure switch which becomes inoperative as soon as it has performed the function for which it is intended.

Other and further features and objects of the invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawing and following specification, wherein are disclosed exemplary embodiments of the invention, with the understanding, however, that such changes may be made therein as fall within the scope of the appended claims, without departing from the spirit of the invention.

In said drawing:

Figure l is a schematic diagram illustrating one embodiment of my invention as it may be applied to a fluid fuel burner, and

Figure 2 is a schematic diagram of another embodiment of my invention in which a nonmetallic casing is employed.

Referring now to the drawing:

The device there shown is particularly suitable for use in connection with equipment for automatic ignition of the pilot flame of a gas burner, as shown in my copending application Serial Number 281,549, but quite obviously may be modified and used for other burners or in any other device in which it is desired to use pressure or pressure differential as a control means.

The mechanism which the switch operates is preferably located within the oven or other burner chamber adjacent the burner. This mechanism, as shown by way of example in the drawing, consists of a pilot burner 24, and a main valve it which controls the supply of fuel to the main burner 28.

The valve control mechanism consists of a body l0 which has a supply inlet in the lower face thereof, indicated at H, which leads into a cylindrical main chamber l2. Concentric with the main chamber I2 is a small inner chamber I3 and interposed between these two chambers is the valve Hi to control the passage of fuel from one chamber to the other. Conduits 48 and 52 lead from chambers 12 and I3 to the switch 31.

Ignition for the pilot burner 24 is furnished by means including an electrode 3|. This elec trode 3| is supported from the base it) by means of a bracket. The electrode is of course insulated from the bracket. Current for causing a high voltage discharge through the gap 33 is furnished by means of the step-up transformer 34.

The switch for controlling the supply of electricity to the step-up transformer 34 is indicated generally at 31. The primary of the stepup transformer is grounded to the body or casing of the switch by means of the terminal 36. A connection is thus made between the terminal 36 and a pool of electrically conductive liquid, such as mercury, and as indicated at 38. An alternative arrangement, indicated in Figure 2, in the event that a non-metallic switch casing is employed, is to directly connect the primary of the transformer to an electrode 39 extending into the mercury pool.

The other side of the primary coil is connected to the secondary 4| of the step-down power transformer 42, power being furnished by means of the line connection 43. The other side of the secondary coil 4! of the power transformer is connected to the central electrode 45 of the switch. This central electrode 45 is, under normal conditions, spaced above the mercury pool 38 so that no electrical contact is made therewith. There are two chambers 44 and 46 within the switch casing, the upper chamber communicating with the lower by means of a tube 41 which projects downward from the upper chamher into the lower chamber and into the mercury pool 38. This tube 41 is preferably of insulating material. The central electrode 45 projects downwardly from the insulated cap 50 to a position within the tube.

The lower chamber 44 is connected by means of the conduit 48 to a channel 49 in the body ID. The switch is located outside of the oven, the conduit passing through the wall 5| of the oven. The conduit or channel 49 within the body I 0 communicates with the chamber l2 and is also connected with the pilot burner orifice 54. When gas under pressure is present in the chamber 12, it will pass outwardly through the restricted orifice 54 and will also set up a pressure in conduit 48 and in the lower chamber 44 of the switch. The upper chamber 45 of the switch is connected by means of the second conduit 52 with the inner chamber 13.

Now it is apparent that when the gas is turned 1 on to supply gas to the burner, it will first pass into chamber l2, and from this chamber will pass upwardly to the pilot burner. Gas will also pass through the conduit 48 into the chamber 44. Illasmuch as this gas is at higher than atmospheric pressure, mercury within the chamber 44 and outside the tube 4! will be depressed to drive mercury up within the tube 41.

Mercury within the tube 41, when it reaches a sufliciently high lever contacts the lower end of the electrode 45 and closes the circuit through the primary of the ignition transformer 34. The high voltage of the secondary winding through electrode 3! causes an arc across the gap 33 to the grounded electrode 30 on the pilot burner 24 to ignite the gas issuing from the pilot. burner.

The heat of the pilot burner will actuate a bimetallic element 2| which will, in turn, open the valve l6 and permit gas to flow into the chamber l3 and thence to the main burner where it is, of course, ignited by the pilot burner. As soon as this main valve opens, the pressure within the chambers l2 and I3 is equalized, and inasmuch as conduit 52 connects chamber l3 in the burner assembly with the upper chamber 46 of the switch, the pressure within the chambers 44 and 46 of the switch will be equalized, which permits the mercury 38 to seek its own level and thus break the contact between the electrode 45 and the mercury 38. Breaking of the primary circuit of the ignition transformer 34 stops the discharge of electricity at the pilot burner 24. It is apparent that the switch is actuated only when pressure is set up by gas admitted to the chamber 12, and that the switch is stopped as soon as pressure is equalized between chambers 12 and I3, which takes place soon after the pilot burner is ignited.

It is preferable that means be provided for varying the position of the electrode 45 relative to the mercury pool 38. I have therefore provided the electrode 45 with an adjusting nut 35 threadedly engaged on the upper end thereof. This construction permits the electrode to be adjusted vertically and it will, of course, be obvious that the higher the electrode is positioned. the greater pressure or pressure differential will be required to close a circuit through the switch.

My invention is susceptible to numerous modifications. I may, of course, utilize only one transformer and pass a volt circuit through the switch, or may eliminate both transformers and pass the current directly through the switch and the electrode 3|. Also means other than those here shown may be used to create the necessary pressure differentials and subsequent equalization,

Such a device is also particularly well adapted for use with control equipment used in connection with processes carried on under pressure or a partial vacuum and over which close control is desirable.

Although I have described specific embodiments of my invention, it is apparent that modifications thereof may be made by those skilled in the art. Such modifications may be made without departing from the spirit and scope of my invention as set forth in the appended claims.

I claim as my invention:

1. Pressure differential responsive switch means comprising a container having upper and lower chambers, a conduit leading from each chamber to conduct a pressure medium, a pool of electrically conductive fluid in the lower chamber, a tube extending from the upper chamber down into the pool of fluid, an electrode extending down through the tube and adapted to make contact with the fluid when pressure in the lower chamber exceeds the pressure in the upper chamber, and means for adjustably securing the electrode within the tube for regulating the operating pressure.

2. In a pressure differential switch, a casing divided into two chambers, a tube projecting from the upper chamber into the lower chamber, an electrode projecting through the tube, a pool of electrically conductive liquid in thelower chamber, means for selectively introducing a pressure medium into either chamber, and means for making an electrical connection with the pool of liquid.

3. In a pressure differential switch comprising a cylindrical container having an upper and lower chamber, means for introducing a pressure medium into the chambers, a pool oi electrically conductive liquid in the lower chamber, a tube extending from the upper to the lower chamber and into the liquid, an electrode extending from the top of the container into the tube and having the upper portion thereof threaded, and a threaded adjusting nut to receive the electrode to regulate the position of the electrode in relation to the pool of liquid.

4. In a pressure differential switch, a container separated into two compartments, :1 tube to extend the upper chamber into the lower chamber, an electrode enclosed within the upper chamber and means for forcing the liquid into contact with the electrode and for subsequently releasing said liquid from its contact.

5. For use in connection with a valve having inlet and outlet chambers, switch means for controlling an electric circuit, said switch means comprising a container, upper and lower chambers in the container, a pool of an electrically conductive liquid in the lower chamber, a tube, the upper end of same connecting with the upper chamber, the lower end of the tube being immersed in the pool of liquid, a terminal making contact with the liquid, an electrode extending. downward through the tube but out of contact with the liquid, means for causing the liquid to rise in the tube to contact the electrode including a conduit for connecting the lower chamber of the switch means with the inlet chamber of the valve, and means for breaking the circuit thus closed including a conduit for connecting the upper chamber of the switch and the outlet chamber of the valve.

6. For use in connectionwith a gas burner having a main burner, a supply line, a safety switch in the supply line, and electrical ignition means for igniting the gas issuing from the main burner, switch means for energizing the ignition means, said switch means including conduits leading from opposite sides of the safety valve, a housing formed to provide an upper and a lower chamber, a tube projecting down into the lower chamber from the upper chamber, an electrode within the tube, and a mercury pool in the lower chamber whereby when a difference in pressure exists on opposite sides of the safety valve, the height of the level of the mercury within the tube and within the lower chamber is varied to cause a circuit to be completed through the electrode and the higher level of the mercury pool.

7. In a fluid-operated electric switch, the combination of a casing divided into an upper and a lower chamber by a Well equipped with a downwardly-directed tube opening through said wall and projecting downwardly into said lower chamber, thereby establishing communication between said upper and lower chambers, an electric-circuit terminal in said tube, an electrically-conductive liquid in said lower chamber normally closing the lower end of said tube and out of contact with said terminal, said liquid being connected to another companion terminal of the circuit of which said first terminal forms a part, and conduit-means connected to at least one of said chambers permitting substantially-equal fluidpressures in said two chambers with said liquid out of contact with said terminal, whereby increase of the fluid-pressure in said lower chamber outside of said tube and above said liquid in excess of that in said upper chamber, by reason of change of pressure in said conduit-means, causes said liquid to rise in said tube and close said electric-circuit between itself and said terminal.

8. The electric switch set forth in claim '7 in which said liquid is mercury.

9. The electric switch set forth in claim '7 in which said conduit-means is connected to said upper chamber.

10. The electric switch set forth in claim '7 in which said conduit-means is connected to said lower chamber at a point outside of said tube and above said liquid,

JOHN C. ENGLISH. 

